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Mitochondrion of the Trypanosoma brucei long slender bloodstream form is capable of ATP production by substrate-level phosphorylation.
Mitochondrion of the Trypanosoma brucei long slender bloodstream form is capable of ATP production by substrate-level phosphorylation.
- Source :
- PLoS Pathogens; 10/11/2023, Vol. 19 Issue 10, p1-31, 31p
- Publication Year :
- 2023
-
Abstract
- The long slender bloodstream form Trypanosoma brucei maintains its essential mitochondrial membrane potential (ΔΨm) through the proton-pumping activity of the F<subscript>o</subscript>F<subscript>1</subscript>-ATP synthase operating in the reverse mode. The ATP that drives this hydrolytic reaction has long been thought to be generated by glycolysis and imported from the cytosol via an ATP/ADP carrier (AAC). Indeed, we demonstrate that AAC is the only carrier that can import ATP into the mitochondrial matrix to power the hydrolytic activity of the F<subscript>o</subscript>F<subscript>1</subscript>-ATP synthase. However, contrary to expectations, the deletion of AAC has no effect on parasite growth, virulence or levels of ΔΨ<subscript>m</subscript>. This suggests that ATP is produced by substrate-level phosphorylation pathways in the mitochondrion. Therefore, we knocked out the succinyl-CoA synthetase (SCS) gene, a key mitochondrial enzyme that produces ATP through substrate-level phosphorylation in this parasite. Its absence resulted in changes to the metabolic landscape of the parasite, lowered virulence, and reduced mitochondrial ATP content. Strikingly, these SCS mutant parasites become more dependent on AAC as demonstrated by a 25-fold increase in their sensitivity to the AAC inhibitor, carboxyatractyloside. Since the parasites were able to adapt to the loss of SCS in culture, we also analyzed the more immediate phenotypes that manifest when SCS expression is rapidly suppressed by RNAi. Importantly, when performed under nutrient-limited conditions mimicking various host environments, SCS depletion strongly affected parasite growth and levels of ΔΨ<subscript>m</subscript>. In totality, the data establish that the long slender bloodstream form mitochondrion is capable of generating ATP via substrate-level phosphorylation pathways. Author summary: In the bloodstream of a mammalian host, proliferating Trypanosoma brucei parasites take up glucose and generate most of their ATP by glycolysis. This is atypical for an aerobic eukaryotic cell, which usually employes mitochondrial oxidative phosphorylation to generate ATP. In this unique case, the mitochondrion of the T. brucei bloodstream form has lost its function as the powerhouse of the cell, and the organelle of the parasite has been considered to be only an ATP consumer. However, we have shown that this is not entirely correct and that the parasite mitochondrion can produce ATP itself by phosphorylation at the substrate level. We have mapped the possible metabolic pathways and identified a key enzyme responsible for this activity: succinyl-coenzyme A synthetase. The importance of this enzyme for parasite viability depends on culture media that mimic different mammalian host environments. Our study offers a revolutionary new insight into bloodstream form mitochondrial metabolism and provides a deeper understanding of the parasite mitochondrion, which is the target of commonly used cationic drugs to treat African Animal trypanosomiasis. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 15537366
- Volume :
- 19
- Issue :
- 10
- Database :
- Complementary Index
- Journal :
- PLoS Pathogens
- Publication Type :
- Academic Journal
- Accession number :
- 172917624
- Full Text :
- https://doi.org/10.1371/journal.ppat.1011699